Get It Right: The Crucial Gap Standards for Fire Doors in the UK

20 September 2024

When it comes to fire safety, the importance of a properly installed fire door cannot be overstated. Fire doors are an essential part of building safety regulations, designed to prevent the spread of fire and smoke, providing crucial time for occupants to escape and emergency services to respond. One of the most critical aspects of fire door installation is ensuring the correct gaps around the door. This guide will help you understand why these gaps matter and how to achieve the proper fit. 

Why Do Gaps Around Fire Doors Matter? 

The primary purpose of a fire door is to compartmentalise a building, containing fire and smoke within a limited area. If the gaps around a fire door are too large, smoke and fire can easily penetrate the door, rendering it ineffective. Conversely, if the gap tolerances are too small, the door may not close properly, compromising its ability to form a seal. Properly sized gaps ensure that the door performs as intended in the event of a fire. 

Understanding UK Regulations 

In the UK, fire doors must comply with specific standards as outlined in BS 8214:2016, which provides recommendations for the design, installation, and maintenance of fire doors. The key regulations concerning gaps around a fire door are focused on the clearance between the door leaf and the door frame or threshold. 

Recommended Gap Sizes 

According to UK regulations, the following are the recommended gap sizes for fire door installations: 

Side and Head Gaps (between the door leaf and the frame): 

  • The gap should be 2 to 4 mm. 
  • A gap of around 3 mm is generally considered ideal. This ensures that the door can close properly while providing an effective barrier against fire and smoke. 

Bottom Gap (between the door leaf and the floor or threshold): 

  • The gap should be 8 to 10 mm if there is no threshold seal. 
  • If a threshold seal is installed, the gap should be reduced to around 3 to 4 mm to maintain an effective seal against smoke. 

Threshold Seal: 

  • A threshold seal is not always required, but when used, it must be tested with the door to ensure compatibility and effectiveness. The seal helps prevent smoke from passing under the door, which is crucial in maintaining the integrity of the fire barrier. 

Installers should always refer to the fire door manufacturer’s installation instructions to ensure compliance. 

 

Tools and Techniques for Measuring Gaps 

To achieve the correct gaps, precise measurement is crucial. Here are some tips: 

  • Use a Gap Gauge: A gap gauge is a simple tool designed to measure the distance between the door leaf and the frame or floor accurately. This tool is essential for ensuring consistency in gap sizes. The FAS Gap Gauges are a set of 4 precision laser-cut stainless steel shims for measuring the gap between a fire door and the frame. The flat shim design prevents the gap from being opened further which can be a drawback of wedge style gauges. 
  • Check with a Feeler Gauge: A feeler gauge can be used to check the uniformity of the gap, particularly for smaller gaps around the sides and top of the door. 
  • Regular Inspections: After installation, regular inspections should be carried out to ensure that the door and gaps remain compliant over time. Wear and tear, as well as changes in building structure, can alter the gap sizes, requiring adjustments. 

 

Common Mistakes to Avoid 

  • Incorrect Door Frame Installation: If the door frame is not installed squarely, achieving the correct gap sizes can be difficult. Always ensure the frame is level and plumb before fitting the door. 
  • Damaged Intumescent Strips: An intumescent strip is a piece of fire-resistant material, which is fitted around a fire door door or frame. In the event of a fire, the strip will expand, preventing the fire from spreading. If this gets damaged, you should replace the full strip around the door or frame. FAS sell a large selection of fire, smoke & acoustic strips to fit all fire door assemblies. 
  • Using Unsuitable Hinges: Fire door hinges must be of the correct size and type to support the door’s weight and allow for the correct gap sizes. Using improper hinges can lead to misaligned gaps. 
  • Ignoring the Bottom Gap: While it might be tempting to overlook the gap at the bottom of the door, this is a critical area where fire and smoke can infiltrate. Always ensure this gap is within the recommended range.  

 

The Importance of Professional Installation 

Given the critical nature of fire doors, professional installation is highly recommended. Certified installers are trained to ensure that fire doors are fitted according to regulatory standards, including achieving the correct gaps. This not only ensures compliance with UK law but also provides peace of mind that the fire door will perform as required in an emergency. 

Remember, a well-installed fire door with the correct gaps can save lives. Always prioritise precision and compliance when installing or maintaining fire doors. 

Get in touch for help on selecting the right fire door products for your project. 

 

Win a Set of FAS Gap Gauges! 

As part of Fire Door Safety Week 2024, we are giving away some of our new FAS Gap Gauges, specifically created to help ensure the critical gaps around fire doors are correctly measured and maintained. 

To enter the giveaway, simply visit our social media channels and look out for the competition post on the 23rd September 2024.  

The competition closes on the 26th September and the winner will be drawn on the 27th September 2024. Good luck!